Hydrogen sulfide is frequently encountered in drilling oil and gas wells. It is corrosive to iron or steel drill pipe and casings. When the drill pipe breaks due to hydrogen sulfide embrittlement, the drilling operation must be interrupted and the drill pipe string repaired, thus increasing the cost of the drilling operation. Hydrogen sulfide is also a pollutant to the environment and a health hazard to drilling personnel.
It has been proposed to use certain specific iron oxides in drilling muds to scavenge hydrogen sulfide released during the drilling operation. For example, in my U.S. Pat. No. 4,008,775, issued Feb. 22, 1977, I described the use of a specific porous iron oxide in drilling mud to scavenge hydrogen sulfide. This iron oxide is described as having an ideal composition of substantially Fe.sub.3 O.sub.4 and a surface area at least ten times as great as magnetite particles of equal size. In my co-pending application Ser. No. 44,026, referred to above, I have further characterized that porous iron oxide as having an amorphous (non-crystalline) moiety of Fe.sub.2 O.sub.3 together with an Fe.sub.3 O.sub.4 crystalline phase. In my application, Ser. No. 963,747, filed Nov. 27, 1978, and now abandoned, I have also disclosed that certain specific iron oxide waste dusts from open hearth or basic oxygen furnace steel-making operations can be used to scavenge hydrogen sulfide in well drilling muds or to scavenge same from hydrocarbon gases. As described in application Ser. No. 44,026, filed subsequently, these iron oxide waste dusts, like the iron oxide described in the aforementioned patent, are also iron oxide particles of large surface area and now are found to have an amorphous moiety of Fe.sub.2 O.sub.3 and an Fe.sub.3 O.sub.4 crystalline phase.